- Email: [email protected]
LVR-15 reactor epithermal neutron beam parameters—Results of measurements
ARTICLE IN PRESS Applied Radiation and Isotopes 67 (2009) S202–S205
Contents lists available at ScienceDirect
Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso
LVR-15 reactor epithermal neutron beam parameters— Results of measurements J. Burian a,, V. Klupak a, M. Marek a, J. Rejchrt a, L. Viererbl a, G. Gambarini b, G. Bartesaghi b a b
Department of Reactor Physics, Nuclear Research Institute Rez, plc, Czech Republic Department of Physics, University of Milan, Italy
a r t i c l e in f o
Keywords: BNCT Epithermal neutron beam Reactor beam dosimetry
a b s t r a c t The epithermal neutron beam of the LVR-15 reactor provides the appropriate conditions for varied BNCT activity. The principal parameters have been frequently determined. The following detectors have been used for the measurement: set of activation monitors of different nuclides irradiated in free beam and in the water phantom, Si semiconductor detector with 6LiF converter, twin ionization chambers, thermoluminescence dosimeters, gel dosimeters used for imaging of separate part of dose, neutron spectrometer of Bonner type. Obtained results of measured parameters are presented in the paper. & 2009 Elsevier Ltd. All rights reserved.
1. Introduction The construction of the epithermal neutron beam at a horizontal channel of LVR-15 reactor, see Fig. 1, was completed in year 2000 (Burian et al., 2001). A group of patients was treated in the project ‘‘Pre-clinical trials of brain tumors’’ (Burian et al., 2002). In the long term the facility at the reactor is utilized for the study of physical and biological aspects of BNCT. In the part of physics the periodic verification of parameters (as international comparison, too) and the development of appropriate dosimetry methods are performed. In the part of biology the biological effectiveness of the beam has been evaluated on different biological models (cell cultures, immature rat brain, mouse intestine crypt regeneration) (Mares et al., 2002).
2. Materials and methods The beam properties were monitored by measurements of the neutron spectrum, neutron profile, fast neutron kerma rate in tissue, and photon absorbed dose. Activation foils: Activation of foil detectors is the basic method used for neutron spectrum determination. During the time standard set of detectors were selected, see Table 1. Neutron spectrum is evaluated using an adjustment procedure (SAND, STAYSWL, BASACF) which provides a means for combination of reaction rates with a calculated neutron spectrum resulting in determining an optimal estimation of the thermal, epithermal and fast neutron fluence rates and their uncertainties. Corresponding author. Tel.: +420 266 172 465; fax: +420 266 172 045.
E-mail address: [email protected] (J. Burian). 0969-8043/$ - see front matter & 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.apradiso.2009.03.050
Semiconductor Si detector with Li converter: Detectors consisted of Si diodes and neutron converters with 6Li are frequently used for measurement of slow neutron fluence. After reaction of thermal neutron with 6Li, triton and alpha particle are produced with total energy of 4.78 MeV (2.73 MeV for triton and 2.05 MeV for alpha particle). The Si diode works as detector of heavy charged particles. When triton or alpha particle hits the PN junction of the Si diode a signal pulse is produced on the output of the detector. From the count rate of the pulses the slow neutron fluence rate is determined. This type of detector can be used for neutron fluence rates roughly from 102 to 1010 cm2 s1. Twin ionization chambers: The neutron kerma rate in tissue and photon kerma rate in tissue both in the beam and in phantom can be determined with twin ionization chambers. They are used either as air-filled or flushed with a TE-equivalent CH4-based gas mixture (TE chamber) or with argon (Al chamber). The chambers are calibrated in the absolute 137Cs radiation beam in the units of the exposure. Responses of the chambers to the neutrons and gamma rays, respectively, are determined from measurements
Fig. 1. The LVR-15 epithermal beam facility.
ARTICLE IN PRESS J. Burian et al. / Applied Radiation and Isotopes 67 (2009) S202–S205
Table 1 Set of activation detectors. Elem.
Mass (mg)
Conc. (%)
Au Au
39.14 42.59
1 1
Cu
292.71
100
In Ni
45.85 37.31 46.39 43.71 562.53 1106.83
Reaction rate (s1)
197Au(n,g)198Au 197Au(n,g)198Au 63Cu(n,a)60Co
8.89E14 8.26E14 –
63Cu(n,g)64Cu
2.92E16
115In(n,g)116mIn
8.72E14
1 0.5 4 1 0.1
115In(n,0 n)115mIn
–
139La(n,g)140La 55Mn(n,g)56Mn 45Sc(n,g)46Sc 186W(n,g)187W 115In(n,g)116mIn
8.18E16 1.11E15 5.21E16 2.91E14 6.52E15
115In(n,0 n)115mIn
2.7E18
58Ni(n,p)58Co
9.52E–19
100 100
using different neutron and gamma sources as follows: 252Cf, 9 Be(d,n), T(d,n). Al–P glass TLD: The standard types of TLD are used to get absolute information about the gamma absorbed dose rate in the BNCT beam and in phantom measurement. The response of the detector lies in the energy range 25 keV–7.5 MeV and the detector can measure the gamma absorbed dose up to 10 Gy. The thermal neutron correction factor derived from the measurement in a thermal neutron field has to be used. Gel dosimeters: The Fricke gel dosimeters that are at the basis of the method are laboratory-made radiochromic gels (Gambarini, et al., 2004); the composition of such gel dosimeters is: Porcine skin in the amount of 3% of the final weight, ferrous sulfate solution [1 mM Fe(NH4)2(SO4)2 6H2O]; sulfuric acid [25 mM H2SO4] and xylenol-orange [0.165 mM C31H27N2Na5O13S]. These dosimeters are produced in form of layers, typically 3 mm thick; they are imaged with a CCD camera system before and after irradiation, and the measured difference of optical density at 585 nm is proportional to the absorbed dose.
3.5x109 3.0x109
Thermal Epithermal
2.5x109 Flux (1/cm2s)
La Mn Sc Ww
46.55
Fast
2.0x109 1.5x109 1.0x109 5.0x108 0.0 0
4
8 Depth (cm)
1.E+09
1.E+08
1.E+07
12
Fig. 4. Neutron fluxes at the water phantom central axis, calculated with MCNP.
Fig. 2. Principal configuration of Bonner spectrometer in one block.
Neutron Fluence Rate per Unit of Lethargy [1/cm2s]
In
Measured reaction
S203
BASACF SAND
1.E+06
1.E+05 1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 Energy [MeV] Fig. 3. Neutron spectrum, the result received with codes SAND and BASACF.
ARTICLE IN PRESS S204
J. Burian et al. / Applied Radiation and Isotopes 67 (2009) S202–S205
Thermal neutrons in water 8
1.6E+09
7
Fluence rate (s-1cm-2)
1.4E+09 Gel with boron Au foils p-n diode (arbitrary units]
1.2E+09
6
1.0E+09
5
8.0E+08
4
6.0E+08
3
4.0E+08
2
2.0E+08
1
0.0E+00 0.0
2.0
4.0
6.0 8.0 10.0 12.0 14.0 Depth in water phantom (cm)
16.0
18.0
0 20.0
Fig. 5. Thermal neutron distribution in water.
Fig. 6. Gel dosimeters in the water phantom.
Fig. 8. 2D representation of the total dose vs. depth, obtained from the image of a gel dosimeter made with heavy water.
Fig. 7. Gel dosimeters after irradiation, placed on the light source for transmittance image detection.
In order to obtain the separate evaluation of the photon (Dg) and recoil proton (Dp) doses, gel dosimeters were prepared in pairs having different isotopic content, that is one using light water (standard dosimeter) and the other heavy water (99.9% pure); in each measurement, two such dosimeters were inserted close to each other in the phantom. This method for separation of fast neutron dose by means of gel dosimeters has been now studied more exhaustively and improved. Bonner type spectrometer: Method based on a positioning thermal neutron detector behind the different thickness of polyethylene. New construction with 7 detectors in one block was tested, principal configuration is shown in Fig. 2. The advantage of the spectrometer is that the 90% response intervals of the spheres continuously cover the epithermal part of
the neutron energy range. Disadvantage of the spectrometer is its high thermal neutron efficiency resulting in the necessity to apply them at low reactor power. The spectrum adjustment procedure is analogical to the case of the activation foils.
3. Results The current free beam integral characteristics are as follows: Epithermal neutron flux 6.5 108/cm2 s Fast neutron flux 5.5 107/cm2 s Thermal neutron flux 3.8 107/cm2 s Photon absorbed dose measured in the beam axis by ionization chamber was 1.98 Gy/h, fast neutron kerma in tissue was 3.5 Gy/h. Results were received for reactor power 9 MW approximately. Neutron spectrum with activation foil measurement is shown in Fig. 3. Standard water phantom (400 mm width, 400 mm height, 300 mm depth) was used for measurement of neutron depth profiles. The result of calculation is demonstrated in Fig. 4.
ARTICLE IN PRESS J. Burian et al. / Applied Radiation and Isotopes 67 (2009) S202–S205
Monoblock neutron spectrometer (MNS) of Bonner type: Response functions have been calculated with MCNP for MNS and verified by measurement with monoenergetic neutrons (Van de Graaf), isotopic sources (PuBe, Cf). The rough form of neutron spectrum was reconstructed from measurement for reactor epithermal beam, see Fig. 9.
100000
10000 [n/cm2.s.kW]
S205
1000
100
4. Conclusions
10
1 1.00E-06
1.00E-04
1.00E-02
1.00E+00
1.00E+02
The epithermal neutron beam of the LVR-15 reactor provides the conditions for varied BNCT activity. The knowledge of the source parameters (energy spectrum and space distribution especially) is necessary requirement for this actions.
Energy [MeV]
References Fig. 9. Neutron spectrum-MNS of Bonner type.
The thermal neutron depth profile measured with activation method, Si–Li detector and gel is shown in Fig. 5. Gel dosimetry: Rectangular Fricke-gel dosimeters (13 15 cm2) were placed in the water phantom perpendicularly to the beam mouth, in order to attain depth dose images. In Fig. 6, a dosimeter ready for the irradiation is shown, and in Fig. 7, a dosimeters after irradiation is visible, settled on the light source for transmittance imaging detection. In Fig. 8, the total doses measured with a gel dosimeter made with heavy water is reported in a 2D representation.
Burian, J., Marek, M., Rataj, J., Flibor, S., 2001. The experience from the construction of BNCT facility at the LVR-15 Reactor, IAEA, Vienna, Austria, June 1999. In: Current Status of Neutron Capture Therapy, IAEA Tec-Doc 1223, pp.126–131. Burian, J., Marek, M., Rataj, J., et al., 2002. Report on the first patient group of the phase I BNCT trial at the LVR-15 Reactor. In: Sauerwein,W., Moss, R.L., Wittig, A. (Eds.), Proceedings of 10th International Congress on NCT for Cancer. Germany, pp.1107–1113. Gambarini, G., Colli, V., Gay, S., Petrovich, C., Pirola, L., Rosi, G., 2004. In-phantom imaging of all dose components in boron neutron capture therapy by means of gel dosimeters. Applied Radiation and Isotopes 61, 759–763. Maresˇ, V., Burian, J., Marek, M., Prokesˇ, K., 2002. Assesment of the relative biological effectiveness of LVR-15 nuclear reactor neutron beam by a simple ´ sti n. L., Stud. Biol. 6, animal model. Acta Universitatis Purkyniana, 2002. U 5–10.
Contents lists available at ScienceDirect
Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso
LVR-15 reactor epithermal neutron beam parameters— Results of measurements J. Burian a,, V. Klupak a, M. Marek a, J. Rejchrt a, L. Viererbl a, G. Gambarini b, G. Bartesaghi b a b
Department of Reactor Physics, Nuclear Research Institute Rez, plc, Czech Republic Department of Physics, University of Milan, Italy
a r t i c l e in f o
Keywords: BNCT Epithermal neutron beam Reactor beam dosimetry
a b s t r a c t The epithermal neutron beam of the LVR-15 reactor provides the appropriate conditions for varied BNCT activity. The principal parameters have been frequently determined. The following detectors have been used for the measurement: set of activation monitors of different nuclides irradiated in free beam and in the water phantom, Si semiconductor detector with 6LiF converter, twin ionization chambers, thermoluminescence dosimeters, gel dosimeters used for imaging of separate part of dose, neutron spectrometer of Bonner type. Obtained results of measured parameters are presented in the paper. & 2009 Elsevier Ltd. All rights reserved.
1. Introduction The construction of the epithermal neutron beam at a horizontal channel of LVR-15 reactor, see Fig. 1, was completed in year 2000 (Burian et al., 2001). A group of patients was treated in the project ‘‘Pre-clinical trials of brain tumors’’ (Burian et al., 2002). In the long term the facility at the reactor is utilized for the study of physical and biological aspects of BNCT. In the part of physics the periodic verification of parameters (as international comparison, too) and the development of appropriate dosimetry methods are performed. In the part of biology the biological effectiveness of the beam has been evaluated on different biological models (cell cultures, immature rat brain, mouse intestine crypt regeneration) (Mares et al., 2002).
2. Materials and methods The beam properties were monitored by measurements of the neutron spectrum, neutron profile, fast neutron kerma rate in tissue, and photon absorbed dose. Activation foils: Activation of foil detectors is the basic method used for neutron spectrum determination. During the time standard set of detectors were selected, see Table 1. Neutron spectrum is evaluated using an adjustment procedure (SAND, STAYSWL, BASACF) which provides a means for combination of reaction rates with a calculated neutron spectrum resulting in determining an optimal estimation of the thermal, epithermal and fast neutron fluence rates and their uncertainties. Corresponding author. Tel.: +420 266 172 465; fax: +420 266 172 045.
E-mail address: [email protected] (J. Burian). 0969-8043/$ - see front matter & 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.apradiso.2009.03.050
Semiconductor Si detector with Li converter: Detectors consisted of Si diodes and neutron converters with 6Li are frequently used for measurement of slow neutron fluence. After reaction of thermal neutron with 6Li, triton and alpha particle are produced with total energy of 4.78 MeV (2.73 MeV for triton and 2.05 MeV for alpha particle). The Si diode works as detector of heavy charged particles. When triton or alpha particle hits the PN junction of the Si diode a signal pulse is produced on the output of the detector. From the count rate of the pulses the slow neutron fluence rate is determined. This type of detector can be used for neutron fluence rates roughly from 102 to 1010 cm2 s1. Twin ionization chambers: The neutron kerma rate in tissue and photon kerma rate in tissue both in the beam and in phantom can be determined with twin ionization chambers. They are used either as air-filled or flushed with a TE-equivalent CH4-based gas mixture (TE chamber) or with argon (Al chamber). The chambers are calibrated in the absolute 137Cs radiation beam in the units of the exposure. Responses of the chambers to the neutrons and gamma rays, respectively, are determined from measurements
Fig. 1. The LVR-15 epithermal beam facility.
ARTICLE IN PRESS J. Burian et al. / Applied Radiation and Isotopes 67 (2009) S202–S205
Table 1 Set of activation detectors. Elem.
Mass (mg)
Conc. (%)
Au Au
39.14 42.59
1 1
Cu
292.71
100
In Ni
45.85 37.31 46.39 43.71 562.53 1106.83
Reaction rate (s1)
197Au(n,g)198Au 197Au(n,g)198Au 63Cu(n,a)60Co
8.89E14 8.26E14 –
63Cu(n,g)64Cu
2.92E16
115In(n,g)116mIn
8.72E14
1 0.5 4 1 0.1
115In(n,0 n)115mIn
–
139La(n,g)140La 55Mn(n,g)56Mn 45Sc(n,g)46Sc 186W(n,g)187W 115In(n,g)116mIn
8.18E16 1.11E15 5.21E16 2.91E14 6.52E15
115In(n,0 n)115mIn
2.7E18
58Ni(n,p)58Co
9.52E–19
100 100
using different neutron and gamma sources as follows: 252Cf, 9 Be(d,n), T(d,n). Al–P glass TLD: The standard types of TLD are used to get absolute information about the gamma absorbed dose rate in the BNCT beam and in phantom measurement. The response of the detector lies in the energy range 25 keV–7.5 MeV and the detector can measure the gamma absorbed dose up to 10 Gy. The thermal neutron correction factor derived from the measurement in a thermal neutron field has to be used. Gel dosimeters: The Fricke gel dosimeters that are at the basis of the method are laboratory-made radiochromic gels (Gambarini, et al., 2004); the composition of such gel dosimeters is: Porcine skin in the amount of 3% of the final weight, ferrous sulfate solution [1 mM Fe(NH4)2(SO4)2 6H2O]; sulfuric acid [25 mM H2SO4] and xylenol-orange [0.165 mM C31H27N2Na5O13S]. These dosimeters are produced in form of layers, typically 3 mm thick; they are imaged with a CCD camera system before and after irradiation, and the measured difference of optical density at 585 nm is proportional to the absorbed dose.
3.5x109 3.0x109
Thermal Epithermal
2.5x109 Flux (1/cm2s)
La Mn Sc Ww
46.55
Fast
2.0x109 1.5x109 1.0x109 5.0x108 0.0 0
4
8 Depth (cm)
1.E+09
1.E+08
1.E+07
12
Fig. 4. Neutron fluxes at the water phantom central axis, calculated with MCNP.
Fig. 2. Principal configuration of Bonner spectrometer in one block.
Neutron Fluence Rate per Unit of Lethargy [1/cm2s]
In
Measured reaction
S203
BASACF SAND
1.E+06
1.E+05 1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 Energy [MeV] Fig. 3. Neutron spectrum, the result received with codes SAND and BASACF.
ARTICLE IN PRESS S204
J. Burian et al. / Applied Radiation and Isotopes 67 (2009) S202–S205
Thermal neutrons in water 8
1.6E+09
7
Fluence rate (s-1cm-2)
1.4E+09 Gel with boron Au foils p-n diode (arbitrary units]
1.2E+09
6
1.0E+09
5
8.0E+08
4
6.0E+08
3
4.0E+08
2
2.0E+08
1
0.0E+00 0.0
2.0
4.0
6.0 8.0 10.0 12.0 14.0 Depth in water phantom (cm)
16.0
18.0
0 20.0
Fig. 5. Thermal neutron distribution in water.
Fig. 6. Gel dosimeters in the water phantom.
Fig. 8. 2D representation of the total dose vs. depth, obtained from the image of a gel dosimeter made with heavy water.
Fig. 7. Gel dosimeters after irradiation, placed on the light source for transmittance image detection.
In order to obtain the separate evaluation of the photon (Dg) and recoil proton (Dp) doses, gel dosimeters were prepared in pairs having different isotopic content, that is one using light water (standard dosimeter) and the other heavy water (99.9% pure); in each measurement, two such dosimeters were inserted close to each other in the phantom. This method for separation of fast neutron dose by means of gel dosimeters has been now studied more exhaustively and improved. Bonner type spectrometer: Method based on a positioning thermal neutron detector behind the different thickness of polyethylene. New construction with 7 detectors in one block was tested, principal configuration is shown in Fig. 2. The advantage of the spectrometer is that the 90% response intervals of the spheres continuously cover the epithermal part of
the neutron energy range. Disadvantage of the spectrometer is its high thermal neutron efficiency resulting in the necessity to apply them at low reactor power. The spectrum adjustment procedure is analogical to the case of the activation foils.
3. Results The current free beam integral characteristics are as follows: Epithermal neutron flux 6.5 108/cm2 s Fast neutron flux 5.5 107/cm2 s Thermal neutron flux 3.8 107/cm2 s Photon absorbed dose measured in the beam axis by ionization chamber was 1.98 Gy/h, fast neutron kerma in tissue was 3.5 Gy/h. Results were received for reactor power 9 MW approximately. Neutron spectrum with activation foil measurement is shown in Fig. 3. Standard water phantom (400 mm width, 400 mm height, 300 mm depth) was used for measurement of neutron depth profiles. The result of calculation is demonstrated in Fig. 4.
ARTICLE IN PRESS J. Burian et al. / Applied Radiation and Isotopes 67 (2009) S202–S205
Monoblock neutron spectrometer (MNS) of Bonner type: Response functions have been calculated with MCNP for MNS and verified by measurement with monoenergetic neutrons (Van de Graaf), isotopic sources (PuBe, Cf). The rough form of neutron spectrum was reconstructed from measurement for reactor epithermal beam, see Fig. 9.
100000
10000 [n/cm2.s.kW]
S205
1000
100
4. Conclusions
10
1 1.00E-06
1.00E-04
1.00E-02
1.00E+00
1.00E+02
The epithermal neutron beam of the LVR-15 reactor provides the conditions for varied BNCT activity. The knowledge of the source parameters (energy spectrum and space distribution especially) is necessary requirement for this actions.
Energy [MeV]
References Fig. 9. Neutron spectrum-MNS of Bonner type.
The thermal neutron depth profile measured with activation method, Si–Li detector and gel is shown in Fig. 5. Gel dosimetry: Rectangular Fricke-gel dosimeters (13 15 cm2) were placed in the water phantom perpendicularly to the beam mouth, in order to attain depth dose images. In Fig. 6, a dosimeter ready for the irradiation is shown, and in Fig. 7, a dosimeters after irradiation is visible, settled on the light source for transmittance imaging detection. In Fig. 8, the total doses measured with a gel dosimeter made with heavy water is reported in a 2D representation.
Burian, J., Marek, M., Rataj, J., Flibor, S., 2001. The experience from the construction of BNCT facility at the LVR-15 Reactor, IAEA, Vienna, Austria, June 1999. In: Current Status of Neutron Capture Therapy, IAEA Tec-Doc 1223, pp.126–131. Burian, J., Marek, M., Rataj, J., et al., 2002. Report on the first patient group of the phase I BNCT trial at the LVR-15 Reactor. In: Sauerwein,W., Moss, R.L., Wittig, A. (Eds.), Proceedings of 10th International Congress on NCT for Cancer. Germany, pp.1107–1113. Gambarini, G., Colli, V., Gay, S., Petrovich, C., Pirola, L., Rosi, G., 2004. In-phantom imaging of all dose components in boron neutron capture therapy by means of gel dosimeters. Applied Radiation and Isotopes 61, 759–763. Maresˇ, V., Burian, J., Marek, M., Prokesˇ, K., 2002. Assesment of the relative biological effectiveness of LVR-15 nuclear reactor neutron beam by a simple ´ sti n. L., Stud. Biol. 6, animal model. Acta Universitatis Purkyniana, 2002. U 5–10.